ATOMIC-LAYER SURFACE-REACTION OF CHLORINE ON SI AND GE ASSISTED BY ANULTRACLEAN ECR PLASMA

Atomic-layer surface adsorption and reaction of chlorine on Si(100) an d Ge(100) as well as Si0.5Ge0.5(100) assisted by low-energy Ar+ ion ir radiation were investigated using an ultraclean ECR plasma system with surface analysis by XPS and FTIR:RAS. Hydrogen termination on Si and Ge prepared by HF-treatment or annealing in H-2 was removed by Ar+ ion irradiation, and that on Ge was removed, while not on Si, only by the chlorine molecular supply. By repeating alternate chlorine molecular supply (greater than or similar to 0.02 Pa.s) and Ar+ ion irradiation (similar to 4 x 10(15) cm(-2)), atomic-layer etching of Si, Ge and Si0 .5Ge0.5 was observed with a saturated etch rate per cycle of 1/4 atomi c-layer thickness. When Ar+ ion irradiation was increased further unde r a condition of saturated chlorine molecular adsorption, the etch rat e per cycle tended to increase with Ar+ ion irradiation up to a satura tion value of the single atomic-layer thickness. The Ge atoms indicate d a higher reactivity than the Si atoms in the atomic-layer etching. ( C) 1998 Elsevier Science B.V. All rights reserved.